1. Field of the Invention
The present invention relates to a programmable modular circuit for detecting telephone tones, which typically vary from one telephone transmission standard to another and from one country to another, and more particularly relates to the detection of identification signals in a digital signal.
2. Discussion of the Related Art
Rockwell Corporation markets detection tone circuits including, three times, the serial connection of a programmable filter, a power estimator, and a comparator. This tone detector has only two programmable configurations. In a first configuration, each of the three filters receives the digital signal to be processed, which allows to detect three different tones. In the second configuration, the three filters are connected in series to detect a tone within a narrow frequency band. This structure is far from being capable of matching all the possible tone detection situations.